A breast X-ray diagnostic apparatus is generally used for a mammography examination upon a breast cancer examination to perform X-ray imaging of a breast of a subject in a two-dimensional image. For many years, an X-ray diagnostic apparatus of this type has been using an analog film (hereinafter referred to as a film) for an image reception system. Furthermore, after performing the X-ray imaging, a two-dimensional image of a breast would be formed on the developed film. As an observation system of the two-dimensional image, an X-ray film illuminator would be used to present the two-dimensional image on a film by transmitting light from a back surface side to a front surface side of a hung film.
However, in recent years, advancement of technology regarding the X-ray diagnostic apparatus has caused changes in the reception system of the X-ray imaging and the observation system of the two-dimensional image. For example, the reception system of the X-ray imaging has been changed so as to use a digital detector such as a computed radiography (CR) or a flat panel detector (FPD) instead of a film. Along with this change, the observation system of the two-dimensional image has been changed so as to display image data obtained by the digital detector on a display such as a monitor instead of the X-ray film illuminator.
Furthermore, in addition to such changes in the reception system and the observation system, an imaging method carried out by the X-ray diagnostic apparatus and a breast cancer detection aiding technique have also made progress. Conventionally, as the imaging method carried out by the X-ray diagnostic apparatus, a system for obtaining a two-dimensional image of a breast of a subject has been used by arranging an X-ray source to perform imaging from a certain angle. In addition to this, recently, the imaging method uses a three-dimensional imaging method (hereinafter referred to as a tomosynthesis) that performs a three-dimensional reconstruction on images obtained by moving the X-ray source to perform imaging from a plurality of angles, and creates a plurality of pieces of tomographic images in accordance with a depth inside a breast. Since the tomosynthesis obtains a tomographic image per depth inside the breast, there is an advantage in that a region that has been difficult to diagnose because of overlapping mammary glands would become easier to observe.
On the other hand, as the breast cancer detection aiding technique, there is a mammography computer-aided detection (CAD) (hereinafter merely referred to as “CAD”). The CAD allows a region of a tumor mass or calcification, etc. that is characteristic of a breast cancer to be detected by computer analysis.
Normally, there is no particular problem with the X-ray diagnostic apparatus mentioned above; however, an inventor of the present invention considers that there is room for improvement in the following points. For example, since a display such as a monitor has a lower density resolution compared to a film, it is unable to sufficiently express thickness information of mammary glands or a pathological abnormality. Therefore, in the case of using a display, since the displayed two-dimensional image is difficult to be observed, there is room for improvement in this respect. This would cause inconvenience in that the diagnosis becomes difficult since a diagnostic reading doctor would find it difficult to determine whether a region of interest in the two-dimensional image indicates overlapping mammary glands or a pathological abnormality. From the perspective of solving such inconvenience, the aforementioned tomosynthesis is used. However, in the case of using the tomosynthesis, since numerous tomographic images are to be read, there is a greater burden on the diagnostic reading doctor, compared to when, conventionally, a piece of two-dimensional image was read; which, in this respect, there is room for improvement. Such respect also applies to a U.S. breast cancer examination work flow. In the U.S. breast cancer examination work flow, a subject receives a breast cancer examination at an image center, and a diagnostic reading doctor (A) at the image center reads all of the tomographic images and sends a report presenting a diagnostic reading result to a diagnostic reading doctor (B) who is a family doctor of the subject. The report includes a character string that describes the diagnostic reading result and a two-dimensional image. The diagnostic reading doctor (B) is not a specialist in diagnostic reading. The diagnostic reading doctor (B) displays the received report. Here, in the same manner as mentioned above, there is an inconvenience for the diagnostic reading doctor (B) in that the displayed two-dimensional image is difficult to observe. From the perspective of solving this inconvenience, even if the breast cancer examination work flow were to be changed to send to the diagnostic reading doctor (B) a plurality of tomographic images regarding the diagnostic reading result from among all of the tomographic images, it would be a great burden on the diagnostic reading doctor (B) because the diagnostic reading doctor (B) is not a diagnostic reading specialist, however, would have to confirm a plurality of tomographic images.
In other words, the conventional X-ray diagnostic apparatus can be improved to solve the points of difficulty in observing the displayed two-dimensional image in the case of using a display, and a great burden on both the diagnostic reading doctors (A) and (B) in the case of using the tomosynthesis.
The object of the present invention is to obtain an easily observable two-dimensional image when being displayed on a display, and to reduce the burden on a diagnostic reading doctor.